Re: Dropping of old loop optimizer

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello,

> > > > I would like to know your opinion on this subject. Why I believe old
> > > > loop optimizer should be dropped as soon as possible:
> ...
> > > The "old" loop optimizer does BIV-to-GIV flattening which is important on
> > > processors without double-register addressing modes such as the SH,
> > > MIPS16, Thumb, and a few others.
> > > 
> > > Does the new loop optimizer support this feature?
> > 
> > no; as I said, anything related to iv's is problem.
> 
> Then I personally (and probably most users of the SH) would prefer the old
> loop optimizer be retained until the new loop optimizer supports BIV
> flattening. 
> 
> This one optimization is extremely important; if we don't have it, the
> compiler will generate a move/shift/add operation for each IV-related
> load/store within the loop, which kills performance.

you perhaps don't understand what I wrote. I have never suggested
dropping the loop optimizer now; I am asking for the best way how to
replace its functionality, so that it can be dropped.

Zdenek